Michigan Compiled Laws, Chapter 123. Local Government § 123.232

Sec. 2. Any 2 or more political subdivisions may contract for the joint ownership, use and/or operation of sewers and/or sewage disposal facilities. Any 2 or more political subdivisions may contract relative to the furnishing of sewage disposal services by 1 or more of such political subdivisions to the other political subdivision or subdivisions. Any such contract shall be authorized or approved by the legislative body of each contracting political subdivision and shall be effective for such term as shall be prescribed therein not exceeding 50 years.